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Numerical simulations of neutral metacommunities are used here to predict the effects of growth and shrinkage of metacommunities, as well as their separation and merging caused by continental collision and rifting and their secondary eustatic effects. Although growth and shrinkage of metacommunities predictably change diversity, separating and merging metacommunities have counterintuitive effects. Separating and merging metacommunities change diversity within the individual areas, especially so for smaller areas, but they cause no change in total diversity of the system, contrary to previous predictions. The response times of metacommunities are likely to be geologically undetectable except for enormously large systems. These models can be used to predict the plate-tectonic effects on the diversity of terrestrial, coastal-marine, deep-marine, and oceanic-island systems. Of these, global and regional coastal-marine systems are the most acutely sensitive to the changes in area and fragmentation caused by plate tectonics. Oceanic-island systems also experience global and regional changes in diversity during supercontinent breakup and assembly, with the global effects driven by the changing length of volcanic arcs, and the regional effects also driven by secondary eustatic changes in shallow-marine area. Although individual terrestrial provinces or continents may experience substantial changes in diversity from rifting and collision, global terrestrial diversity should be unchanged except for the relatively modest contributions caused by the secondary eustatic effects on land area. These changes in diversity may be reinforced or counteracted by the changing latitudinal position of metacommunities.

The widespread occurrence of stratigraphic sequences suggests that a large fraction of the stratigraphic record is systematically biased. For example, sequences in landward areas tend to have more symmetrical transgressive-regressive records as well as hiatuses of long duration. Sequences in shelf settings have highly asymmetrical regressive-dominated records, with relatively minor hiatuses and condensed sections. Deeper settings tend to have more symmetrical transgressive-regressive records, with significant condensed sections. This stratigraphic bias can both mask true paleontological patterns and create apparent patterns.

Sequence architecture implies that environments are continually changing, whether this change is obvious in lithofacies or not. Given that facies control has been documented in many benthic taxa as well as in planktic/nektic/nektobenthic groups that are biostratigraphically important (e.g., conodonts, ammonoids, and graptolites) continuous change in lithofacies suggests that faunas should continually change upsection–and that this change should reflect changing environments, not in situ evolution. Vertical changes in taxonomic composition and morphology are more easily explained as clines or ecophenotypic gradients, rather than as evolutionary sequences. Because stratigraphic sequences cause vertical facies successions to be repeated, fossil morphologies should repeatedly appear within a section, with their occurrences separated by a hierarchy of gaps, varying in scale from short-term taphonomic-bias gaps through parasequence-scale gaps to sequence-scale gaps. Morphotypes with stratigraphically discontinuous ranges commonly have been named separately despite the morphological similarity at different horizons, and in some cases, this pattern has been interpreted as iterative evolution. However, sequence architecture and facies control could easily produce this pattern. It is argued here that the Lazarus Effect of Jablonski is far more pervasive than previously acknowledged and can occur at a range of scales from a variety of processes.

The juxtaposition of dissimilar facies at sequence boundaries can produce apparent paleontological events, while facies control will mask true paleontological events. Apparent first occurrences will be concentrated immediately above sharp facies contacts at sequence boundaries, whereas apparent last occurrences will be concentrated immediately below sequence boundaries. However, a true first occurrence within a section will inevitably be delayed from the true first occurrence within the basin because of facies control; likewise, true last occurrences within a section will precede the true last occurrence within a basin. The magnitude of this delay/precedence will vary with the position of the section within the basin. The asymmetric sequences of midshelf settings can cause a delay of up to one full sequence; more symmetrical sequences of landward and basinward settings can create a of up to approximately one-half of a sequence.

What can be done about this source of bias? One solution is to create a tight eventstratigraphic correlation network in conjunction with a basin-wide array of sections to be able to track any given facies through time and space. A second solution, useful where such correlations are not possible or such an array of sections is not available, would be to compare within-habitat faunal and morphologic change between sequences.

Possibly the most intriguing possibility is that the same processes that create stratigraphic sequences also drive macroevolutionary change through geologically rapid reassortment of sedimentary environments and the redistribution of barriers to isolation.

Understanding the drivers of macroevolutionary trends through the Phanerozoic has been a central question in paleobiology. Increasingly important is understanding the regional and environmental variation of macroevolutionary patterns and how they are reflected at the global scale. Here we test the role of biotic interactions on regional ecological patterns during the Mesozoic marine revolution. We test for escalatory trends in Jurassic marine benthic macroinvertebrate ecosystems using occurrence data from the Paleobiology Database parsed by region and environment. The escalation hypothesis posits that taxonomic groups that could adapt to intense predation and bioturbation proliferated, whereas groups unable to adapt were reduced in diversity and abundance or driven to extinction. We tested this hypothesis in five regions during Jurassic stages and among four depositional environments in Europe. Few escalatory trends were detected, although at least one escalatory trend was observed in every region, with the greatest number and strongest trends observed in Europe. These trends include increases in shallow infauna and cementing epifauna and occurrences of facultatively mobile invertebrates and decreases in pedunculate, free-lying, and sessile epifauna. Within Europe, escalatory trends occur in shallow-water environments but also in deeper-water environments, where they are predicted not to occur. When regional trends are aggregated, trends in Europe drive the global signal. The results of this study suggest that while evidence of escalation is rare globally, it is plausible that escalation drove macroevolutionary patterns in Europe. Furthermore, these results underline the need to dissect global fossil data at the regional scale to understand global macroevolutionary dynamics.

Although provinces are widely used to delimit large-scale variations in biotic composition, it is unknown to what extent such variations simply reflect large-scale gradients, much as has been shown at smaller scales for communities. We examine here whether four previously described Middle and Late Ordovician provinces on Laurentia are best described as distinct provinces or as biotic gradients through a combination of the Paleobiology Database and new field data. Both data sets indicate considerable overlap in faunal composition, with spatial patterns in Jaccard similarity, quantified Jaccard similarity, and nonmetric multidimensional scaling ordination structure that correspond to variations in substrate type, specifically from carbonate-dominated strata in western Laurentia to mixed carbonate–siliciclastic strata in the midcontinent to siliciclastic-dominated rocks in easternmost Laurentia. Because sampling was limited to shallow-subtidal settings, this gradient cannot be attributed to variations in water depth. Likewise, geographic distance accounts for only a quarter of the variation in faunal composition. This cross-continent faunal gradient increases in strength into the early Late Ordovician, and appears to represent increased siliciclastic influx into eastern Laurentia during the Taconic orogeny. These results raise the question of whether biogeographic provinces may be in general better interpreted and analyzed as biotic gradients rather than as discrete entities.

Biotic invasions in the fossil record provide natural experiments for testing hypotheses of niche stability, speciation, and the assembly and diversity of regional biotas. We compare ecological parameters (preferred environment, occupancy, median abundance, rank abundance) of genera shared between faunal provinces during the Richmondian Invasion in the Late Ordovician on the Laurentian continent. Genera that spread from one faunal province to the other during the invasion (invading shared genera) have high Spearman rank correlations (>0.5) in three of four ecological parameters, suggesting a high level of niche stability among invaders. Genera that existed in both regions prior to and following the invasion (noninvading shared genera) have low correlations (<0.3) and suggest niche shift between lineages that diverged at least 8 Myr earlier. Niche shift did not accumulate gradually over this time interval but appears to have occurred in a pulse associated with the onset of the Taconic orogeny and the switch from warm-water to cool-water carbonates in southern Laurentia.

A drawback to most existing methods of calculating confidence limits on fossil ranges is their assumption that the probability of collecting a taxon through a stratigraphic section is constant. Marshall (1997) described an approach that would circumvent this problem, but it requires knowing the probability of collection as a function of stratigraphic position. Multivariate paleoecological methods, such as detrended correspondence analysis (DCA), offer a means of estimating these probabilities. DCA axis 1 sample scores can be used to quantify facies change through a stratigraphic section, and to calculate the probability of collection of a taxon relative to DCA axis 1. From these two, the probability of collection of each taxon can be estimated for each horizon in the measured section. This approach is applied here to the Upper Ordovician Kope Formation of the Cincinnati, Ohio, area to distinguish between disappearances of taxa that are driven by facies change and taxon rarity and those that represent true regional extinction. This new approach to confidence limits could also be applied to test the synchroneity of extinction or origination at large-scale turnover events, such as mass extinctions and the turnover pulses that bound episodes of faunal stasis.

A basic hypothesis in extinction theory predicts that more abundant taxa have an evolutionary advantage over less abundant taxa, which should manifest as increased survivorship during major extinction events and longer fossil-record durations. Despite this, various paleontologic studies have found conflicting patterns, indicating a more complex relationship between abundance and extinction in the geologic past. This study tests the relationship between abundance and extinction among brachiopod genera within seven third-order depositional sequences spanning the Late Ordovician to Early Silurian (Katian–Aeronian) of the Cincinnati Arch.

Contrary to predictions, abundance is not positively correlated with duration in this study. Abundance and duration range from strongly negatively correlated to uncorrelated depending on the spatial scale of analysis and the geologic intervals included, but correlations never indicate that abundance is an evolutionary advantage. In contrast, abundance was an advantageous trait prior to the Ordovician/Silurian extinction, and brachiopods with higher abundances were more likely to survive the event than less abundant brachiopods. While this result is in keeping with common models of extinction, it has not been observed previously at a mass extinction boundary. This may be further evidence that the Ordovician/Silurian extinction was not accompanied by a shift in the macroevolutionary selectivity regime.

If your undergraduate experience in stratigraphy was anything like mine, it was overwhelmingly dull. It was all about nomenclature and classification and endless lists of formation names. There were apparently no questions to be asked and the goal of stratigraphy was to devise boxes into which to place all types of geologic data. Notwithstanding the important work of correlation, the perception was that it was the sedimentologists who did the real science, science that focused on the processes of sediment accumulation and their controlling factors. Since then, stratigraphy has undergone a conceptual revolution, and it is necessary to examine how the field has changed and what those advances mean for paleobiology.

Long-term diversity equilibria, ecological incumbency, and widespread recurrent fossil assemblages have each been cited as evidence that local processes, such as competition, played an important role in structuring communities over geologic time. We analyze the relationship between local and regional diversity in tropical marine communities spanning approximately 13 Myr of the Late Ordovician to test for the role of local processes in structuring local communities. We find a significant and strong positive relationship between local and regional diversity, indicating that local communities were not saturated with species and that local processes did not exert a dominant influence on local diversity. Rather, local diversity was influenced more by regional oceanographic processes that governed the size of the regional species pool. This evidence for unsaturated communities is consistent with the Walker and Valentine hierarchically structured niche model of global diversification. These results come at the beginning of the 200-Myr Paleozoic plateau in both local and global diversity and therefore raise the question whether local communities were ever saturated with species during the Paleozoic. Similar studies need to be conducted during other times in the Paleozoic to determine if this is indeed the case.

Analysis of a global elevation database to measure changes in shallow-marine habitat area as a function of sea level reveals an unexpectedly complicated relationship. In contrast to prevailing views, sea level rise does not consistently generate an increase in shelf area, nor does sea level fall consistently reduce shelf area. Different depth-defined habitats on the same margin will experience different changes in area for the same sea level change, and different margins will likewise experience different changes in area for the same sea level change. Simple forward models incorporating a species-area relationship suggest that the diversity response to sea level change will be largely idiosyncratic. The change in habitat area is highly dependent on the starting position of sea level, the amount and direction of sea level change, and the habitat and region in question. Such an idiosyncratic relationship between diversity and sea level reconciles the widespread evidence from the fossil record for a link between diversity and sea level change with the lack of quantitative support for such a relationship throughout the Phanerozoic.

Niche conservatism is increasingly recognized in diverse modern ecological settings, and it influences many aspects of modern ecosystems, including speciation mechanisms, community structure, and response to climate change. Here, we investigate the stability of niches with benthic marine invertebrates along a Late Ordovician onshore-offshore gradient on the Cincinnati Arch in the eastern United States. Using a Gaussian niche model characterized by peak abundance, preferred environment, and environmental tolerance, with these parameters estimated through weighted averaging and logistic regression, we find evidence of strong niche conservatism in peak abundance and preferred environment, particularly for abundant taxa. This conservatism is maintained in successive depositional sequences and through the nearly 9–10 Myr study interval. Environmental tolerance shows no evidence of conservatism, although numerical simulations suggest that the error rates in estimates of this parameter are so high that they could overwhelm evidence of conservatism. These numerical simulations also indicate that both weighted averaging and logistic regression produce useful estimates of peak abundance and preferred environment, with slightly better results for weighted averaging. This evidence for niche conservatism suggests that long-term shifts of higher taxa of marine invertebrates into deeper water are primarily the result of differential rates of origination and extinction. These results also add to the evidence of long periods of relatively stable ecosystems despite regional environmental perturbations, and they constrain the causes of peaked patterns in occupancy.

A compilation of species occurrences in a chronostratigraphic framework of depositional sequences from a 250,000 km2 area in the eastern United States is used to test for coordinated stasis in Middle and Upper Ordovician articulate brachiopods. Two rapid pulses of turnover in brachiopod species separate three periods of relatively lower turnover (ecologic-evolutionary [EE] subunits) that range from 3 to 9 m.y. in duration. Turnover within these EE subunits is characterized by high levels of percent species origination (ca. 60%) and percent species extinction (ca. 80%) and low levels of percent species persistence (<10%), all of which fall outside the range reported for coordinated stasis. Turnover between EE subunits is characterized by low levels of percent species holdover and percent species carryover (ca. 10% or less) and is consistent with coordinated stasis, although turnover pulses are driven largely by pulses in either extinction or origination, and not by pulses in both, as reported for coordinated stasis. Taken together, although these data display a marked bimodality in turnover, high levels of turnover within EE subunits is inconsistent with a pattern of coordinated stasis. Turnover rates within these EE subunits are much higher than previous global estimates for Cambro-Ordovician brachiopods or Phanerozoic marine species and indicate that local extirpation and migration play a significant role in regional biodiversity dynamics. Despite the high level of turnover observed within these EE subunits, some level of ecologic stability occurs because abundant genera persist throughout entire EE subunits. Ordovician species in this study behaved relatively independently of other taxa and were not tightly integrated as suggested by the broadly overlapping taxon abundance curves, the shifting habitat preference of some taxa, the piecemeal turnover between EE subunits, and the continuous creation of new species associations due to background levels of turnover within EE subunits. Turnover within EE subunits was associated with relatively stable or only mildly fluctuating environments. Rapid turnover between EE subunits was caused by extreme perturbations to the regional or possibly global ocean-climate system.

In several increasingly realistic steps, a model of the stratigraphic distribution of fossils is presented. The first and simplest step assumes that if a taxon was extant it will have been preserved. The second step admits that if a taxon was extant, there is some probability less than one that it will have been preserved. This step produces randomly distributed gaps, and fossil ranges that are somewhat shorter than the span of time in which a taxon actually lived. The third step assumes facies-controlled taxa and parasequence-style cyclicity. This produces randomly and nonrandomly distributed gaps, including the anomalously long gaps recognized in confidence limit studies. The final model incorporates depositional sequences and indicates that first and last occurrences will cluster at sequence boundaries and at flooding surfaces in the transgressive systems tract. Across-shelf gradients in diversity, taphonomy, or eurytopy can control the strength, but not the stratigraphic position of these peaks. Comparison of the model to data from the Upper Ordovician suggests that these modeled features are present in the fossil record. Many previously studied paleobiologic patterns may be, at least in part, an artifact of facies control and sequence architecture. Such patterns include gradual or stepwise mass extinction, punctuated morphologic and taxonomic change, iterative evolution, and the replacement of shallow water faunas by deeper water faunas at biomere boundaries.